Inclined rotary vacuum filter



Dec. 22, 1953 R. J. JoHANsEN 2,663,432

INCLINED ROTARY VACUUM FILTER F/iled May 19, 1950 2 Sheds-Sheet l Dec. 22, 1953 R. J. JoHANsEN 2,663,432

INCLINED ROTARY VACUUM FILTER i Filed May 19, 1950 E Sheets-Sheet 2 Patented Dec. 22, 1953 ZRolf sumar Johansen, Karlstad. sweden assigner it Messsage-t fxsmyr, Karina-a, sweats, a

company of Sweden applicati@ May i9, 195o, Serin it'att `crsims.-priority,fmnication 'sweden May 12s. 11949 8 laiins.

The :present invention relates to a vacuum filter for dewatering and/or for washing cf-cellu'- lose pulp, which lter consists of -a vatfor a sus"- .pension of cellulose .pulp and of 'a rotary 'sieve drum Apartially immersed therein and yhaving nl 'trate compartments 4on vits inner side for the drainage ot ltrate in the 'axial vdirection of the drum.

The main object `of the invention is `to provide a lter in which the r'.dltrate iiows rapidly out of said compartments.

Another object is to provide a filter in which the ltrate compartments slope towards the outlet in all their working positions.

A further object v'of the invention is to provide a lter having a reduced orosei-sectional area ofsaid compartments.

A still further object is to simplify the iilter design and reduce the cost of manufacturing the same.

An important object of-the invention is the provision of a washing lter in which different fractions of ltrate may lbe collected separately without intermixing.

Another object is to reduce the injurious ai-r space within the lilter, thereby improving the suction elect and counter-acting the tendency of foaming present when the iiltrate consists of black liquor.

With these and other objects in View the invention resides essentially in that the axis of the sieve drum is arranged inclining at an angle to the horizontal plane.

The invention will now be more vclosely described with reference to the accompanying drawings. Fig. 1 is a vertical sectional view of a iirst embodiment of the filter according to the invention, and Fig. 2 is an elevational view thereof taken from the 'outlet end and shown l1: `artly in section along the line II-II in Fig. l. Fig. 3 is a vertical sectional view of a second embodiment.

In Figs. 1 and 2, designates a concrete vat having a horizontal bottom and vertical side walls, which vat may either be cast integrally with the foundation or permanently placed thereupon in the shown., accurately horizontal position. Said vat is meant to contain the cellulose fibre 'suspenl' sion that is to be dewatered and washed by the lter. The normal level yof the 'libre suspension in the vat is designated by I3.` A sieve `drum |5 partially immersed into the fibre suspension is rotatably supported by the side walls of the vat. Said sievedrum consists of a perforated cylindrical shell |1 and end walls I9, 2|. The end wall 2| has a concentric opening vbordered bya (ci. 21o-to2) cylindrical kaange `n. A seal-ing tape r25 forms a seal between said ange on the turning drum end wall 2| and an v'adjacent flange 26 forming a part of a stationary `supporting structure 21 which is mounted upon the vat and partly protrudes into the drum through the central opening in the end wall 2|. Within the sieve shell the drum is provided with a concentric cylindrical inner shell 29 and an linner end wal13l.. lThe shell -29 andthe end walls I9., 3| form a closed chamber filled with air of atmospheric pressure. The annular space between the sieve shell l1 and the nonperforated inner shell 29. is divided by radial partitions 33 into a great -number of shallow compartments 35 extending axially along the inside of the sieve shell. At their left-hand ends said compartments are closed, and, at their righthand ends they are provided with short radially directed extensions 3 having inwardly facing outlet openings 31. During the rotation of the drum said outletsnpass successively over two collecting h'oppers 395,9 rigidly secured to the supporting structure?. 21. Said hODpCIS have separate outlets 43,'45 leadingthrough the structure 21, and Y an outlet 46wis also provided from the space between the end walls 2 l, 3| to the outside. On the outside of the supporting structure ll said three outltsare connected rto a suction device, e. g. a vbarometric legroz'j a vacuum pump. Therefore, in operation of theuilter lthe cells 35 and said space between the walls 2 I', 3| are .held under a sbatmospheric pressure. Pulp which `is col'- lcted on .the outside of the Asieve shell due to the inwardly` directedsuction is discharged by a discharge roll 5D and a scraper 52. The outlets 3'! Opposite the discharge roll lare blanked off from the vacuum in the drum. by means of `a stationary shoe `5ft, whereby the pulp layer is vmore easily removed. Sprinkle i tubes 41, 49 for supplying washing liquid are arranged near the outer side of the sieve drum. Y

. The shaft 5j of ,thesieve drum is journalled in two bearings 53, 55., the bearing at the outlet end of the drum being positioned at a lower level than thebearing 5 5 lat the opposite end of the drum. The level difference between the bearings is so `great that the inclination of the shaft lwand of the axis of thek drum amounts to about 2 degrees. Said inclination relatively to the horizontal Vplane has .proved to give a `suli'iciently rapid discharge of tlieiiltrate entering the compartments., so that the 'filtrate that is sucked oi the pulp layer deposited on the sieve surface of the `liltler and that enters into a particular compartment when thesame takesthe position above the hopper 39, actually runs down into said hopper and is not delayed so as to partially run intothe hopper 4l instead. In certain instances an inclination angle of 4 to 5 may be of advantage. With such a small inclination of the drum the axially directed pressure on the bearings 53, 55 is rather insignificant, so that normal bearings may be used, but if necessary, vbearings specially designed for resisting axial thrust may be substituted.

The magnitude of the inclination is dependent upon the length of the filter drum, the speed g thereof, the number of filtrate fractions to be collected separately, etc., but needs hardly in any case exceed 1 to 5, i. e. the tangent for the angle of inclination is equal to or less than 1/5. As another extreme, inclination values of 1 to 50 or less have too small an effect on the drainage to be used. In lters of common sizes and types the inclination of the drum axis preferably lies between 1 to 30.A With an inclination of 1 to l5 the inclination of the hypotenuse of a'triangle is meant, having a horizontal side measuring inches and a vertical side measuring 1 inch.

The inclination angle is a1, and

. l tall a1=-5 From a trigonometric table one finds 'that a1 is 1120. Similarly, with an inclination of 1 to 50, one means an inclination angle,rthe tangent of which is i. e. tan a2=0.02, which gives a2=110.

As shown in Fig. 1, the drum is immersed into the pulp suspension over a part of the periphery which is greater at its outlet end than at its opposite end. As a consequence thereof the pulp layer deposited on the sieve surface is gradually thicker towards the outlet end of the drum. In order to eliminate disadvantages on account thereof, according to the invention measures' are taken to counteract such uneven depositing. rFor instance, diluting liquid may be introduced into the vat at its right-hand end in order to main*- tain diierent pulp concentrations along the length of the drum, the concentration decreasing towards the outlet end, whereby the pulp deposit will be uniformly thick in spite of the fact that the drum is immersed to a greater depth and therefore a greater quantity of liquid filters through the same at the outlet end than elsewhere.

Fig. 3 shows a filter of a design essentially similar to the filter according to Figs. 1 and 2. However, in this embodiment of the invention the drum is supported by the vat Walls in the usual manner with both ends located equally high relatively to the vat, but the filter as a whole is placed in an inclined position. The desired inclination is caused by spacer blocks 57 placed underneath the vat at the end opposite to the outlet end of the drum. By changing the number or the height of the blocks the inclination may easily be adapted to working o-r other conditions and the most favorable angle of inclination may be found out experimentally.

In order to counteract uneven pulp depositing, the vat'which is made of sheet metal, is provided with partitions 59 placed at right angles to the axis of the drum and extending close up to the rotary sieve shell. Said partitions make it possible to maintain a stepped pulp suspension level 4 in the vat, so that the depth of immersion of the drum is essentially the same along its entire length.

I claim:

1. In a vacuum filter, a rotary drum mounted on a substantially horizontal axis of rotation and comprising a cylindrical perforated shell and suction compartments having a uniform cross section and extending parallel to the axis of rotation along the inner side of said shell, said drum being mounted in its working position with one end in a higher position than the other end relative to the horizontal, and suction compartment outlets in the lower end of the drum, whereby all suction compartments slope towards their outlet ends.

2. A Vacuum filter comprising an open top vat adapted to receive a fibre suspension, a rotary f lter drum mounted on a substantially horizontal axis of rotation and having a cylindrical perforated shell and axially extending suction compartments at the inner side thereof, said suction compartments having a uniform depth substantially over their entire length, said drum being mounted in an inclined position in said vat relative to the horizontal so as to extend partially above the top of the vat and partially immersed into the fibre suspension therein, one of the ends of the drum relative to its axis of rotation being immersed to a greater depth than the other, and a plurality of outlets for the compartments at the lower end of the drum.

3. A iilter for dewatering and washing fibrous pulp comprising a rotary cylindrical sieve drum mounted on a substantially horizontal axis of rotation and adapted to receive a, layer of wet pulp to be carried thereby, separate filtrate compartments extending along the inner surface of said sieve drum in the axialdirection thereof and having outlets at a lower end of the sieve, said suction compartments having bottom and side partitions parallel to the axis of 'rotation of the drum, means adapted to connect said compartments to a vacuum means, a plurality of stationary hoppers each with an outlet for collecting different filtrate fractions discharged through said rst-mentioned outlets, and means mounting said sieve drum for rotation about its axis forming a slight angle relative to the horizontal, thus providing lower and upper ends.

4. A filter as claimed in claim 3, in which the inclination of the axis of the cylindrical sieve is of a magnitude in which the angle between the axis of the rotation of the cylindrical sieve drum zlinldythe horizontal plane lies between 1120 and 5. A filter as claimed in claim 3, in which the axis of rotation of the sieve drum forms an angle of 2 to 5 degrees relative to the horizontal.

6. In a vacuum filter, a sieve drum comprising a rotary shaft mounted at an angle of approximately 1120' to 110' relative to the horizontal so that one end of the drum is higher than the other end relative to the axis of rotation, an outer cylindrical perforated shell, an inner cylindrical shell concentric to'said outer shell, a plurality of radial partitions between said outer and inner shells dividing the annular space therebetween into axially extending compartments, a drum head closing said two shells at the higher endand attaching them to the shaft,l an inner drum head closing the end of the inner shell at the lower end and attaching the ,sameV to the shaft, an outer drum head joined to the lower end of the outer shell and having a central aperture, a stationary structure extending through said aperture in the outer drum head and being sealed thereto, and a filtrate collecting hopper between said inner and outer drum heads at the lower end and supported by said stationary structure, said stationary structure having passages therethrough for connection of said hopper and of the space between said inner and outer drum heads to an exterior vacuum generating device.

7. In a vacuum filter, an open top vat adapted to receive a fibre suspension, a rotary sieve drum mounted on a substantially horizontal axis of rotation and extending partially into the vat for partial immersion into said suspension in a position inclined relative to the horizontal, an angle of approximately 1120' to 110, means for connection to a means for maintaining a sub-atmospheric pressure within said drum, outlet means at the lower end of the drum, and partitions in 20 said vat for maintaining a higher level of fibre suspension at one end of the vat than at the other relative to the horizontal.

8. A vacuum lter as claimed in claim 7, in which the vat is provided with transverse partitions arranged close to the bottom part of the sieve drum.

ROLF J OMAR J OHANSEN References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 785,531 Weller Mar. 21, 1905 869,720 Matthias Oct. 29, 1907 1,085,547 Couper Jan. 27, 1914 1,667,465 Wait Apr. 24, 1928 1,748,081 Reed et al. Feb. 25, 1930 1,805,499 Schur May 19, 1931 1,859,642 Woodworth May 24, 1932 1,995,904 Sherman Mar. 26, 1935 2,263,168 Dorr et al Nov. 18, 1941 2,510,254 Richter June 6, 1950 

